es6 check if undefined code example

Example 1: javascript if undefined

if(typeof comment === 'undefined') {

  alert('Variable "comment" is undefined.');

} else if(comment === null){

  alert('Variable "comment" is null.');

}

Example 2: test if is undefined javascript

let id;

if(typeof id === 'undefined') {
    console.log("id is undefined...");
}

Example 3: how to check if object is undefined in javascript

if (typeof something === "undefined") {
    alert("something is undefined");
}

Example 4: js check if undefined

let foo = undefined
//will return true
typeof foo === 'undefined'

Example 5: javascript check undefined

if(myVar === null) {
	console.log("Element is undefined");
}

Example 6: undefined javascript check

if(undefinedElement === null) {
	console.log("Element is undefined");
}